In reprisal for a deadly terrorist attack in Kashmir, the Indian government says it will divert river waters that downstream Pakistan has been counting on.

With tensions rising between India and Pakistan in the wake of a deadly terrorist attack earlier this month that killed more than 40 Indian police officers in Kashmir, New Delhi has decided to retaliate in part by cutting off some river water that flows downstream to Pakistan. The decision to build a dam on the Ravi River, whose waters are allocated to India by treaty but a portion of which had been allowed to flow through to Pakistan, adds an extra source of conflict between two nuclear-armed neighbors that have repeatedly clashed over the disputed Kashmir territory.

To understand the issue better, Foreign Policy spoke with Sunil Amrith, a professor of South Asian studies at Harvard University and the author ofUnruly Waters, a look at how water shapes South Asia’s history, politics, and economic development.

Foreign Policy: India and Pakistan were torn apart at Partition, including critical water resources that had been shared under British India; is this the mother of all transnational water conflicts?

Sunil Amrith, a professor of South Asian studies at Harvard University (Stephanie Mitchell/Harvard University)

Sunil Amrith: It probably is, at least in the suddenness, the arbitrariness, and the brutality with which it emerged. In Asia, many of the other transnational water conflicts were slower to escalate—for example, it wasn’t until the 1980s that neighboring states had the capacity or the ambition to dam and divert the upper reaches of the Himalayan rivers. In terms of the numbers of countries and interests at stake, the Mekong is perhaps the ur-transnational water conflict in Asia, but in the sense of a conflict that was created with the stroke of a pen, the conflict over the Indus delta is quite distinctive.

FP:From the vagaries of the monsoon and famines in the colonial period to the development and dam-building boom in the Jawaharlal Nehru years, how central is control of water to India’s concept of nationhood, especially under Prime Minister Narendra Modi?

SA: The control of water has long been central to many visions of freedom and nationhood in India; that is one of the key arguments in Unruly Waters. This goes back to at least the late 19th century, when a diverse group of Indian nationalists, British water engineers, and administrators began to see irrigation as India’s salvation. The dam-building boom of the Nehru years epitomized the ambitions of a proud post-colonial state and its planned conquest over the vagaries of nature and climate. Nehru famously called large dams the “temples of the new India.”

Under Modi, the control of water has continued to be of symbolic value. The government has also committed itself to the gigantic river-linking project, at an estimated cost of at least $90 billion. But none of this started with Modi. I think in terms of their approach to water management, there is a long thread of continuity across the past several Indian governments.

FP: In this case, India seems to be exercising its legitimate claim to the waters in the Ravi. Do you see this escalating, to the point that India starts to infringe on Pakistan’s allocated waters in the western rivers or even abandons the Indus Water Treaty altogether? What happens if it does?

SA: The World Bank-brokered IWT of 1960 is a paradox: It is touted by many scholars of international relations as an example of successful cooperation between hostile states, and at the same time it’s a frequent target of complaints from politicians on both sides of the border.

Following the failure to broker a deal where India and Pakistan would manage the water resources of the basin collectively, the Indus Treaty sought to legislate their division: The waters of the Sutlej, the Beas, and the Ravi were awarded to India; and the west Indus, the Jhelum, and the Chenab to Pakistan.

In practice, a significant quantity of water flowed into Pakistan even after India’s extraction of what water it needed from the eastern rivers. But this is now in question, as India has vowed to impound more water from the Ravi River. Interestingly, one factor that stopped India doing this earlier was internal conflict over the river’s use between the Indian states it flows through. We must always remember that conflicts over water in South Asia are intra-national at least as much as they are international. This is unlikely to change anytime soon.

There have been periodic calls in India for a unilateral withdrawal from the Indus Treaty, a threat that was issued last in 2016. So far, this has not led to action, and things have settled back into an uneasy coexistence. I would like to think that both sides have too much to lose from the unraveling of these delicate arrangements for the brinkmanship to be pushed too far. But given the global slide to unilateralism and the heightened tension the region, there is always the possibility of strident rhetoric provoking a conflict over water, a conflict in which the real losers will be local people on both sides of the border.

FP:Pakistan is a seriously water-stressed nation already. How serious are the implications for Pakistan of diversions of water flow?

SA: Pakistan is one of the most water-stressed countries in the world. One recent estimate suggests that Pakistan will face a shortage of 31 million acre-feet of water by 2025. [Pakistan uses about 104 million acre feet every year for agricultural irrigation.] Its underground aquifers are critically depleted from the over-extraction of groundwater, and the two largest dams—the Tarbela and the Mangla—have seen a decline in their storage capacity due to excessive deposits of silt. As such, any diminution in water flow will have serious consequences for the livelihoods of Pakistan’s farmers, who have already faced, over the past few years, a dearth of fresh water during the critical season—just before the monsoon, when the summer crop is planted.

FP: Given where the rivers are, is this dispute best understood within the context of the Kashmir conflict, or just a legacy of the Partition?

SA: Both. One reason why Partition so immediately created a water conflict in the Indus basin is that it was already one of the most thoroughly engineered hydraulic systems in the world at that time. But Kashmir was crucial to the conflict from the very outset—something that Daniel Haines’s excellent book, Rivers Divided, shows very clearly. The waters of the Chenab and the Jhelum—awarded to Pakistan under the IWT—flow through Indian-administered Kashmir before they flow into Pakistan. This meant that negotiations over water were always bound up with concerns over territorial sovereignty—and it is one reason why tensions in Kashmir very quickly escalate conflicts over water, as has happened in this case.

FP: India isn’t just an upstream nation, with respect to Pakistan. It’s downstream from China. What are the prospects, given Chinese hydropower development in the Tibetan basin, that there are further transnational water conflicts, with dire impacts downstream?

SA: More than 400 dams are under construction, or planned for the coming decade, in India, Nepal, Bhutan, Pakistan; many more will be built across the Chinese border in Tibet. If the plans come to fruition, this will be among the most heavily dammed regions in the world. These schemes both aggravate international tensions and carry grave ecological risks, which themselves respect no borders. To the same extent that India fears Chinese ambitions to dam the Brahmaputra in particular, Bangladesh has already felt the negative effects of India’s hydraulic engineering upstream.

Having said this, I am always reluctant to draw too direct a line between water scarcity and political conflict—either across or within borders. Conflicts over water are inextricably bound up with politics at every level from the local to the regional. The specter of “water wars” is a blunt tool with which to capture the unpredictability of struggles over water. The existential importance of water might defuse conflict as much as competing attempts to control water will deepen it.

FP:Climate change threatens Tibetan Plateau water resources in a couple of ways—more rainfall in the medium term, but also quicker glacial melts and less water flow in the future. How much could climate change aggravate the already tense cross-border water situation?

SA: The recent Hindu Kush Himalaya Assessment suggests that, even with a drastic reduction in carbon emissions, one-third of the Himalayan glaciers are doomed to melt by the end of this century; without a reduction in emissions, that grows to two-thirds. The livelihoods of well over a billion people are directly at risk from this. Most studies predict that, after an initial period of augmented river flow due to glacial melt, the rivers will begin to dry up for part of the year from 2050 or 2060, putting at risk the food security of a significant portion of humanity. The threat of further conflict as a result is multifaceted. Reduced flow will lead to energy as well as water shortages. The increasing prevalence of extreme precipitation events, also widely predicted, will threaten the stability of the dams, with grave risks downstream.

The report on the glaciers made the headlines, in a few places, for a day or two. It staggers me that this isn’t the biggest news story in the world at the moment.